Apparatus for producing calcium sulphite



Feb. 27, 1940. G. HAYwOOD APPARATUS FOR PRODUCING CALCIUM SULPHITE original Filed nec. s. .19:54

' Patented Feb. 2K7, 194(k)` om'rso*STATES a Y A 2.191,14@` y APPARATUS FOR 'PRoDUcING CALCVUM 1 Gerald Haywood, Westernport, Md., assignor, by

mesne assignments, toWest Virginia Pulp. &' `Paper Company, New Yor k,N. AY., a ycorporation of Delaware original application Deeeiiibeif s; 1994, serial' No.v v

.756,631. Divided'l and thisapplication March' 1s, 1996. serial No. 6 11939 This'invention relates to the production" of calcium sulphite, more particularly in a iinely divided., light precipitated stage. It has to-do With `the apparatus used for this purpose. The 5. present application is a division of rmy pending applicationSerial No. 756,63l led December 8, .1934,"and is a continuation inpart of my appli-y f cation Ser. No. 660,032`yi1ed March 8, 1933', now

Patent Ne. `1,984,1s8,=en1 ineiudes 'a divisible .10 part of the invention disclosed in said applicay 121011,- L Y. e

.It hasbeen a particular object of the invention lto produce `finely divided calcium sulphite in suchl a state and in such an inexpensive and ef- J15 cient`-manner, with lthe requisite degree civ purity, Vto enable its use as an inert iillingagent in avariety of dierent products. In the proper Aconduct ofthe present process it is possible Vto.

produce the material with a substantially :2D form particle size of approximately two microns. This makes the product exceptionally satisfac-V tory as aller for high-grade papers vanda ller or main'ingredient of a coating forming part of coated papers. It may also be used in paints and 25 a variety of other products requiring line iillers.

Briefly, the preferred methodr of forming the improved product involves bringing into "intimate relation a fine mist or spray of milk of lime and an atmosphere rich in sulphur dioxide. The milk fof lime may be produced in any suitable way, 'as byburning limestone to formlime and then slaking the latter' to provide a susf pension of desired concentration. This is then whipped or otherwise formed into a ne spray 1 in an atmosphere having a high percentage of l, sulphur dioxide, preferably formed yby burning sulphur.

eral stages, preferably with continuous circulation of the suspensionnbetween a tank andan W40 absorber or 'reaction vessel' in each stage. The

resulting `suspensionl of calcium sulphite' will be4 somewhat acid due to the presence of sulphury dioxide in solution. k'lhisinay be neutralized in any'convenient Way by the addition Qfja suitable alkali.` To eliminate particles lof grit and the like, the .product may be screened either before or after neutralization. f

' In lieu of employing milk of lime the original 50 calcium carbonate, suchfras limestone, maybe iinely ground and placed in suspension for direct reaction with the sulphur dioxide. Lime mud may, if desired, forma cheap source `for the calcium carbonatexused.l 'I'he reaction in this ,u case proceeds by the replacement vof .the carof sulphur dioxide'in'the reacting atmosphere. If a Weak milk *offlime suspension vis employed,4

i shown. i

The reaction f to produce calcium sulphite in this way may be conducted in' one or sev- 9,433'. Renewed May 19,

' 7 claims. (chase-260) 1* A n,

"fbonateradical by the sulphite radical. Furc .'thermore, the atmosphere containingsulphur dioxideneednot be vderived from the burning of ,sulphur but'ma'y be simply the Waste gases `ol? some industrialpoperationsin which afair percent-age of. sulphur dioxide isdevelopedf For best results and the i'inest'particle size it is desirable to employ a`,concentrated milk of lime suspensionand a relatively highpercentage there isa tendency to produce a crystalline strucftu're of rather 'largeparticle size.

With theoregoin'g object'sf advantages and general mode of'operation'in view, an 'illustrative 115 y form of the improved apparatus for carryingfout the purposes stated will -noW be described in detail in conjunction with the accompanying draw- 'ing` inwhich the 4'apparatus is diagrammatically Vlteferring nowto thefd'r'awinga tank` l0 indicated at the extreme -riglitl'land end of the iigure is arranged to receive aV charge of lime from .any suitable source. `It vInlay be assumed, for

example, that this lime is produced by the ap- ,V25v

"propriate burning ofwlimestone in a kiln, not

illustrated. As previously stated, the process maybe so conducted as to react sulphur dioxide v,directl'yiwith calcium carbonate. Inthat event `thecharge introduced into the tank IU will bea aof iin'ely ground limestone rather than lime. i Water fis introduced into the tank through a 'pipe I'I while an appropriate amount of steam maybe supplied through apipe l2 to facilitate the slak- The mixturev of Water and `lime' or'lime- ,35 stone is thoroughly mixed by vmeans of any suit- Aable form `of agitation-such 'jas' indicated at I3. lThe vapors generated due to `the slaking loffthe lime and the' introduction otA the steam maybe withdrawn through a yvent Iii. .,Whenever' re- 40 quired, the tank may-be completely drained and cleaned through the use of a drainage pipe` l5.

Alter the limefhasbeen thoroughly slaked, or the limestone hasfbeen put into suspension in thewater, the mixture is withdrawn, as by means ,45'

tinued by means of an agitator 20. If desired, the Valves in the lines I1 and I8 may each be partially open so that one portion of the suspension will be returned to tank` I0 while another portion will. be passed into the tank I9 in the manner explained. A suitable drain 2| at the,

I9 enables the complete bottom of the tank drainage and cleaning out of this tank.

A pump 22 serves to draw the'milkof lime from the bottom of ytank I9 and pass it through a. line 23 to the top of a suitable screen 24. This may be of any suitablemesh, say, about i mesh, and will serve to separate the larger particles of grit and lime or limestone from the finer suspension. The latter, passing through the screen, enters a pipe 25 `by which it may be passed either through a line 216 back to the ta nkr I9 or through a line 21 to another tank 28. The

valves shown in the lines 26 and 21 may be suit-1 ably operated to control the iiow of the material, as desired. Ordinarily the material will be passed' through the line 21 so long as the rest of the equipment is capable' of handling the material so supplied. The larger particles passing Dif at the endof the screen '24 may be returned through a line 29 to the tank I9 or may be kpassed to the sewer, or any other point of disposal, through a line 30.

Within'the tank 28 the screened milk of lime is agitatedfurther by meansofan agitator 3l.

kA pump 32 -serves vto withdraw the` material from the bottom of the tank and pass it through aline .In the preferred construction the liquid suspension is maintained at a comparatively low level within the absorber 31 so that a relatively llarge gas space'is provided above the surface of the liquid. An'agitator 38having a series of arms rapidly rotated through' the liquid by a `motor (not shown) or other suitable means,

serves to vigorously agitate the liquid and throw the latter,` in the formof a ne'mist, into the gas space. It will be understood that this gas space will be supplied with an atmosphere containing a relatively high 'percentage of sulphur dioxide, by means to be later explained. This results in a reaction between the milk of vlime or'the'limestone suspension and the sulphur `dioxide by virtue of' which calcium sulphite is produced. The level of the Aliquid in the absorber 31 'is governed'by a barile 39in an outlet b'ox 4D. As the liquid passes over the bafi lie, it enters the pipe 4I, by which it is returned to the tank 28;

Accordingly, in the operation of the system the liquid suspension is continuously circulated through the absorber 31 until the reaction producing calcium sulphite has vbeen carried on toa desirable extent. At this time the valve in the `line 35may be closed andthe valve in theA line 311 may be opened so that the partially converted material in tank 28 is passed to the absorber 36.

j Within Ithe absorber 36 an agitator 42, similar to the agitator 38, is provide-d to whip the suspension into a fine-mist so'that the reaction with the sulphur dioxide may be carried on to com- *sulphur vdioxide in solution.

pletion. A part of the liquid is continuously withdrawn from the absorber 36 at the outlet box 43, which is connected by a line 44 with a tank 15. i An agitator `16, within the latter, serves to continue the stirring kof marquis@ maintain the fine particles in suspension. A pump 31 continuously withdraws liqudfrom the bottom of the tank 45 and passes it through a line 4S to the ous circulation of the liquid is maintained between the absorber 36 and the tank 45.

Whenv thereaction between the milk of lime vor limestone suspension and sulphur' dioxide is substantially complete, the mixture may be Withdrawn from the outlet box 43 through a line 49 communicating with a tank 50. Valves in the Vlines 44 and 49 may be suitably adjusted for this intake ofthe'absorber 33. In this Way continuliquid and'gas.A This reaction may suitably be carried on to the extent of' about 40% completion upon each pass through the absorbers. lIf the material i's circulated at such a rate that about three hours are required to complete a pass, the entireoperation upon agiven batch will take about eight hours. This is a satisfactory rate for fine particle production.4 The reaction should be permitted to continue until the suspension in the absorber 36 becomes slightly acid, indicating the presence of an excess of At this time the `material should be passed from the absorber to the tank 50, as indicated. When all-ofv the lmaterial has been passed from the tank i5 `through absorber 36 and into tank 59, the material from tank 28 will ordinarily be diverted from the absorber 31 to absorber 36 in the manner explained. In this way an appropriate proportion of the reaction 4will take place in each stage.

, Since the material in the tank 5B is in an acid condition, it will be preferable to iormithis tank of wood, or other acid-resistant material, while the remaining tanks may be formed-of steel.

" The suspension of the fine particles is maintained in the tank 50 by an agitator 5I. In this vtank the calcium-sulphite is preferably neutralized by the introduction of a suitable quantity 'of an'alkali, such as caustic soda, calcium carbonate, or milk-fof lime. saryjto add a great deal of alkali since' the ma- It will not be necesterialY isl only slightly acid and only Ysulcient 'alkali to make the material neutralshould be which passesfit through a line 53 to a screen 54; The latter may be of any suitable construc- 'tion,preferably of the gyratory type and preferably of a "relativelyne mesh, for example 200 mesh.- `4The screened material may be passed throughfeitherf or .both of lines 55 and 56 to tanks51 and 58. In these tanksthe materialis also continuously `stirred by agitators 59. .and 63. Ordinarilythe tanks 51 and 58 will be used alternately so that one may i be` in operation while the other is being cleaned. A pump 6I `is arranged to communicate with both ofthe tanks 51 and 58, either jointly or singly, to withdraw the calcium sulphite and pass it through a line 62 to a paper machine, or any other suitable point of disposition, `If the material is to be shipped,v it should -rst be Adewatered'to Ireduce it to a thick'paste or a dry po'wder'."A -However, if it is tofbeused `near the source of manufacture ina watery suspension, it may beused directly as it appearsin tanks 5'!v and'58.,

Now, to provide the desired atmosphere richr in sulphur dioxide in the absorbers;` a sulphur burner 53, of any suitable form,is preferably employed. vSulphur Amay vbe supplied-in any convenient way toy a hopper ltd associated with the burner. The sulphur in anely f divided state will ordinarily descendthrough a seriesl of grids into a stream of air supplied through the inlet 65. Ignitionof thesulphur will take' place in thev burner 63 and the mixture of ignited 'sulphur and air will be drawn orforced into a combustion chamber 65. Abaiiie member ilwithin ythe lattervcauses the mixture of air #and sulphur to follow the path indicated bythe arrow and upon substantial completion of the combustion, the

. products will be withdrawn `from thefbottom' of the chamber into the bottom of a tower @58,I In

rising through the latter, -the .combustion gases 'Will be cooled to a certain extent and ,will then vbe passed through la pipe -dto the. top of the absorber 35. The gasso supplied will be be- `tween- 7 and 20% sulphur dioxide and will be admirably suited for the process.l At the opposite end of this absorber 36 a duct 'ld is pro,n vided toconvey thegas to .the absorber 3l. A pipe y7l then connects thel opposite end of this absorber with anv exhaust pump '12v which discharges the gas through a pipe 'i3 into` the at'- mosphere or into anysuitabie disposal system.

-It'will be understoodthat a large portion of Athe l sulphur dioxide will bewithdrawn `from the gas by the reactions in the absorbers 36 and 3l.

' Itis believed that the operation of the system disclosed in the drawingwill .be clearv from the foregoing. yIf milk .of lime is used as the agentV to react with the sulphur dioxide, .it should preferably be maintained ata` concentration'of about 110 grams of lime per. litre.` This may, of course,

' be lvaried but it has been found that a relatively high concentration of the character mentioned is best suited for the production', cf ajuniformly line product. Reasonably goodV results may be obtained fromthe use of between 1/2`and 1?/2 pounds of lime per gallon of water and quantities even outside of these limits are notto be considered outside vof the scope of the present invention. It is not necessary to cool the' products of the reaction in the absorbers and, in fact, a finer product appears to result from the produc-.-

to introducing the gases into the absorberA at a ytemperature of between400 and' 550 C. The combustion of the sulphur may be arrested and the gases cooled to a limited extent, if desired, adjacent the discharge end of the combustion chamber G6 by introducing water through a pipe 15. If water is introduced into the'tower 68 or the chamber 6, this may be withdrawn from the bottom of the tower 68 through.` a line 16 discharging through a water seal provided by a small tank 11. l

' "The Vcalcium sulphite vmanufactureda in accordance with the present inventionhas a whiteness closely approaching that of magnesium carbonate, whichis normallyrused as-a standard of comparison inthe evaluation `oi? whiteness. y The vcalcium sulphiteihas a reflectionfactor of more than 98% and it :reflects all portions of `lthe spectrum equally Well. .'Iher'e is noselectiveabsorption to detracti'fromthe whiteness of `reflected white light. The improved product, furthermore, may beinadeextremely fine vand of highly vuniform particle size.4 `If .theapparatus is `properly operated -the `major portion of thepartic'les, even as high as may be produced with a diameter of' substantially two microns and practically none oftheparticles-'will exceed .5 microns; The neness .of the product may be further demonstrated by .a `floulk test.'1n 1atest of .this `sort iive gramskof the ne calcium sulphite were shakenv up in 100` c. c xofa .l%-starch solution and'vallowed to stand for 24lhours; thevolumefof' the Asettled particles at the endl of thatperi'od was 17; c.'c.

A' corresponding amount of nely divided clay under the 'same conditions settled clown to `8 sc. c. It will be apparent from this that Y.a product which settles less than .to 10c. c;

under the conditions mentioned is extremely ne,

' i. e., liner than the ordinary clay zliller.` l'

From 'the standpoint of'y opacity the new prod.- uct. is also noteworthy. .By the use o'ffa Konig- Martens polarization 'photometer the percent opacityhasbeen determined `for eachl of` a series of films `of calcium. sulphite `formed, by drying down a suspension onza plate and having vweights ofk 45, 4lbs.22.5 lbs., 11.25'1bs.,'9 lbs., 4.5 lbs.,and v.2.f25'lbs., based upon 500sheets of 25 X-33vdimension. The calcium sulphite used in these tests .was produced under the preferred conditionsmentioned from'milk'oflime containing `100 grams of lime per litre.. The total of the six perac en'tages so determined Agave an opacity 'figure of 38.4., Avi-inely divided clay `filler under thesame conditions gave ancpaciby ligure -of 338.'..The fine calcium sulphite, therefore, was nearly 14% mcreopaque their,tmcfclanh` While an illustrative `form ofA apparatus and preferred mode of operation have been described in considerable de-tail, vitwill be understood that numerous' variations may be made in both without departing'fromA the general spirit and scope of the invention. When reference is madeherein or in the claims to a lime bearing suspension or a suspension of a lime bearing substance,l it should be understood to include not only vmilk of lime but 'a suspension of calcium carbonate, or the like, as well.- l

WhatIclaimis:v A f I. 1.` In apparatus for -producing calciumsulphite ak plurality 'ofA absorption chambers, a plurality. of

.tanks associated with said absorption chambers,

means for delivering a lime bearingsuspension to one of said tanks, means forV continuously recirculating said suspension between said one tank and one of said chambers, means lfor delivering said suspension from said one tank to the other Aof said chambers, means for conveying the suspension from said other chamber to another of saidtanks, means for introducingsulphur dioxide into said chambers, and means vfor .whipping the suspension into aspray in said chambers.

2. In apparatus for producing calcium sulphite a plurality of absorption chambers, aplurality of tanks associated with said absorptionchaml bers, agitating meansin each of said tanks, means for delivering a lime bearing suspensionto onev miy of said tanks, means for continuously recirculating said suspension betweensaid one tank and one of said chambers, means for delivering said suspension from said one tank to the other of said chambers, means `for continuously recirculating the suspension between said other chamber and the other of said tanks, means for introducing sulphur dioxide into said chambers, and means for whipping the suspension intoa spray in said chambers.

3. Iny apparatus for producing calcium sulphite a plurality `of absorption chambers, a plurality of tanks associated with said absorption chambers, means for delivering a lime bearing suspension to `one of said tanks,.means for continuously recirculating said suspension between said one tank and one of said chambers, means for delivering said suspension fromsaid one tank to the other of said chambers, means for continuously recirculating they suspension between said other chamber and another of said tanks, means for introducing sulphur dioxide into said chambers, and means for generating a spray of said suspension within said chambers.

4. In apparatus for producing calcium sulphite a plurality of absorption chambers, a plurality of tanks associated with said absorption chambers, means for delivering a lime bearing suspension to one of said tanks, means for continuously recirculating said suspension between said one tank and one of said chambers, means for delivering said suspension from said one tank to the other of said chambers, means for continuously recirculating the suspension between said other chamber and another of said tanks, means for introducing sulphur dioxide into said chambers, means for generating a spray of said suspension Within said chambers, and means for delivering said suspension from said other chamber into a third one of said tanks.

5. In apparatus for producing calcium sulphite' a plurality of absorption chambers, a plurality of tanks associated with said absorption chambers, means for delivering a lime bearing suspension to one of said tanks, means for continuously recirculating said suspension between said one tank and one of said chambers, means for delivering said suspensionvfrom4 said one tank to the other of said chambers, means for continuously recirculating Ithe suspension between said other chamber and another of said tanks, means for introducing sulphur dioxide into said chambers, and meansfor continuously agitating the suspension. while in said chambers and tanks.

6. In apparatus for producing calcium sulphite a plurality of absorption chambers, agitating means within each of said chambers for` producing a ne liquid spray therein, means for introducing a lime bearing suspension into one of said chambers, means communicating with each of said chambers constructed and arranged for continuously circulating the suspension by Withdrawing it from and returning it to the chamber, means connected with the last mentioned means communicating with said one of said chambers for transferring said suspension .to the other of said chambers, a tank connected between each of said circulating means and its communicating chamber for retaining the greater bulk of the suspension being circulated outside of said chambers, means for burning sulphur, and means for conveying the products of combustion thereof to said chambers successively.

7. In apparatus for producing calcium sulphite, a plurality of absorption chambers, a plurality of tanks, a iluid conduit connecting one of said tanks with one of said chambers, and a return conduit connecting said one chamber with said one tank, said conduits being constructed and arranged to provide means for continuously recirculating a lime-bearing suspension between said one chamber and said one tank, a third conduit connecting said one tank to another of said chambers, and a conduit connecting said other vchamber'with another of said tanks, a gas duct arranged to introduce sulphur dioxide into said chamber, and means for whipping the suspension into a spray in said chambers.

` GERALD I-IAYWOOD. 

